Glaucoma

What is Glaucoma?

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Glaucoma is the term applied to a group of eye diseases that gradually result in loss of vision by permanently damaging the optic nerve. Damage to the optic nerve is generally(but not always) caused by high pressure inside the eye. The high intraocular pressure (IOP) is transmitted to the optic nerve where it can gradually damage the nerve fibers. If the pressure is left untreated the nerve fibers eventually die causing loss in the peripheral vision. Over time untreated pressure can result in complete loss of vision.

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Early detection and treatment is essential to prevent severe visual loss and blindness. Unfortunately, you cannot feel the pressure that causes glaucoma. You need to have regular eye exams to check the pressure and the health of the optic nerve.

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Glaucoma is the second most common cause of vision loss in seniors in Canada. More than 250,000 Canadians have chronic open-angle glaucoma, the most common form of the disease.

What are narrow angles?

Narrow angles occur when the iris, or coloured part of the eye, becomes positioned closer to the cornea, potentially closing the area where the fluid normally drains out of the eye.

This can lead to an emergency situation called closed angle glaucoma which has to be urgently treated with a laser iridotomy.

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How is my eye monitored for glaucoma?

The eye is monitored regularly by your ophthalmologist. The frequency of office visits depends on the stability of the pressure control They will follow the eye pressure, the shape of the optic nerve head (ie. The size of the disc “cup”) and the results from visual field testing, OCT and HRT tests.

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How is glaucoma treated?

Treatment of glaucoma relies on lowering the eye pressure to a normal range and keeping it there with use of eye drop medication, laser treatment or surgery.

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What are the different types of glaucoma?

There are many different types of glaucoma. Most, however, can be classified as either open angle glaucoma, which are usually slowly progressive or angle-closure (closed angle) glaucoma which can present abruptly or progress slowly.

Open-angle glaucoma

Primary open-angle glaucoma (POAG) is by far the most common type of glaucoma. In Canada it accounts for 90% of glaucoma cases. Its frequency increases with age, because over time the drainage mechanism of the eye may become less efficient. The pressure within the eye, therefore, builds up painlessly and without symptoms. Vision loss is not obvious until late in the disease when the central vision is permanently affected

Normal tension glaucoma

is a variant of primary chronic open-angle glaucoma. This type of glaucoma is thought to be due to decreased blood flow to the optic nerve. This condition is characterized by progressive optic-nerve damage and loss of peripheral vision (visual field) despite intraocular pressures in the normal range. This type of glaucoma can be diagnosed by repeated examinations by the eye doctor to detect nerve damage or visual field loss.

Secondary open-angle glaucoma is another type of open-angle glaucoma. It can result from conditions such as: eye trauma, ocular inflammation (iritis), cataracts, diabetes and steroid medications. The treatment for the secondary open-angle glaucomas vary, depending on the cause.

Pigmentary glaucoma

is a type of secondary glaucoma that is can occur in younger individuals. It can be inherited. Due to a particular configuration of affected eyes, pigment from the iris is rubbed off and dispersed into the fluid within the eye. These pigment granules can block the drainage system of the eye. The blocked drainage system leads to elevated intraocular pressure, which results in damage to the optic nerve.

Pseudoexfoliative glaucoma

is another type of secondary glaucoma. This type of glaucoma is characterized by deposits of flaky material on the front surface of the lens (anterior capsule) and in the drainage system of the eye. The accumulation of this material is believed to block the drainage system of the eye and raise the eye pressure. While this type of glaucoma can occur in any population, it is more prevalent in older people and people of Scandinavian descent. It is a systemic condition and recently has been associated with hearing loss in affected individuals.

Angle-closure glaucoma

In angle closure glaucoma the iris (the colored part of the eye) is pushed or pulled up against the drainage channel at the angle of the anterior chamber of the eye. When the iris is pushed or pulled up against the drainage system the fluid (aqueous humour) that normally flows out of the eye is blocked the pressure within the eye increases.

If the angle closes suddenly, symptoms are severe and dramatic. This is called Acute Angle Closure Glaucoma. Immediate treatment is essential to prevent damage to the optic nerve and vision loss. If the angle closes intermittently or gradually, angle-closure glaucoma may be having no symptoms until vision is severely affected.

People who are farsighted (hyperopic) are at an increased risk for acute angle-closure glaucoma because their anterior chambers are shallow and their angles are narrow.

Angle-closure glaucoma tends to affect people born with a narrow angle. People of Asian and Eskimo ancestry are at higher risk of developing it. Increasing age and family history are risk factors. It may be acutely triggered by medications that can dilate the pupils. This condition can also occur spontaneously in a darkened environment when the pupil automatically dilates to let in more light.

An attack of acute angle-closure glaucoma may be associated with headache, a severe red and painful eye, nausea and vomiting and blurred vision. In addition, the high intraocular pressure leads to corneal swelling, which causes the patient to see haloes around lights. Acute angle closure glaucoma is treated initially with topical and oral medications. The definitive treatment is usually laser surgery. In this procedure, the doctor makes a small hole in the iris with a laser (laser iridotomy) to re-open the drainage system and allow the fluid to resume draining into its normal outflow channels.

What are the risk factors for glaucoma?

family history of glaucoma

age

higher than normal intraocular pressure

suspicious optic nerve

thin corneas

myopia (nearsighted)

african heritage

Asian heritage (angle closure glaucoma)

use of medications such as steroids

history of trauma to the eye

systemic vascular disease

Treatment of Glaucoma

The mainstay of glaucoma treatment is to lower the eye pressure, either with eyedrops laser or surgery. A reasonable initial approach would be to choose an eyedrop that will get the eye pressure as low as safely possible in each particular patient. The choice of the initial agent is guided by the patient characteristics and associated medical conditions and the known side effects of each medication. Each patient must then be monitored routinely to ensure that IOP is maintained at a level low enough to prevent glaucomatous progression. If additional eye pressure lowering is required then it is best to add an eyedrop with a different mechanism of action than the initial drug.

If drops fail to maintain the pressure at the desired level laser (selective laser trabeculoplasty) can be performed. If both laser and medications are ineffective the patient may undergo glaucoma surgery (trabeculotomy).